1. Field of the Invention
The present invention relates to a blood reservoir.
2. Description of the Related Art
For example, in open heat surgery, an extracorporeal blood circulation is performed in such a manner that blood is drawn off from veins (large veins) of a patient, gas change is performed on the blood by an oxygenator, and the blood is returned to the arterial system of the patient by driving a blood pump.
An extracorporeal blood circulation system includes a main circuit having a blood return line from large veins and a blood return line to the arterial system, a suction circuit for suctioning blood accumulated in a surgical field, and a vent circuit for suctioning blood accumulated in a heart.
In these suction and vent circuits, blood suctioned from the surgical field (outside the heart) and vented blood suctioned from the interior of the heart are introduced into a blood reservoir (cardiotomy reservoir) for temporarily storing the blood suctioned from these regions. A filtering member provided in the blood reservoir filters off foreign substances from the blood and removes bubbles from the blood. The blood which has undergone filtering and bubble removal in the blood reservoir is returned to the body of the patient. The blood reservoir also has a buffering function for constantly maintaining the blood return rate by regulating the blood volume in the circuits.
In blood caused to flow into the above-described blood reservoir, blood suctioned from the outside of the heart contains comparatively large amounts of foreign substances such as fat droplets, tissue fragments, denatured proteins and aggregates other than the ordinary blood contents. On the other hand, blood vented from the interior of the heart ordinarily has smaller contents of such foreign substances and is less damaged and generally the same as blood drawn off from large veins.
The conventional blood reservoir is constructed such that blood suctioned from the outside of the heart and blood vented from the interior of the heart are filtered by a common filtering member after their confluence in the blood reservoir. Before and during the passage of the vented blood through the filtering member in the blood reservoir, therefore, the least damaged vented blood contacts foreign substances filtered off from the suctioned blood and becomes activated by reaction with the foreign substances.